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Methylcobalamin deficiency type cblE(HMAE)

MedGen UID:
344640
Concept ID:
C1856057
Disease or Syndrome
Synonyms: HMAE; Homocystinuria-Megaloblastic anemia due to defect in cobalamin metabolism, cblE complementation type; HOMOCYSTINURIA-MEGALOBLASTIC ANEMIA, cblE COMPLEMENTATION TYPE; HOMOCYSTINURIA-MEGALOBLASTIC ANEMIA, cblE TYPE; VITAMIN B12-RESPONSIVE HOMOCYSTINURIA, cblE TYPE
SNOMED CT: Methylcobalamin deficiency type cblE (1296847007); Functional methionine synthase deficiency type cblE (1296847007)
Modes of inheritance:
Autosomal recessive inheritance
MedGen UID:
141025
Concept ID:
C0441748
Intellectual Product
Source: Orphanet
A mode of inheritance that is observed for traits related to a gene encoded on one of the autosomes (i.e., the human chromosomes 1-22) in which a trait manifests in individuals with two pathogenic alleles, either homozygotes (two copies of the same mutant allele) or compound heterozygotes (whereby each copy of a gene has a distinct mutant allele).
 
Gene (location): MTRR (5p15.31)
 
Monarch Initiative: MONDO:0009354
OMIM®: 236270
Orphanet: ORPHA2169

Disease characteristics

Disorders of intracellular cobalamin metabolism have a variable phenotype and age of onset that are influenced by the severity and location within the pathway of the defect. The prototype and best understood phenotype is cblC; it is also the most common of these disorders. The age of initial presentation of cblC spans a wide range: In utero with fetal presentation of nonimmune hydrops, cardiomyopathy, and intrauterine growth restriction. Newborns, who can have microcephaly, poor feeding, and encephalopathy. Infants, who can have poor feeding and slow growth, neurologic abnormality, and, rarely, hemolytic uremic syndrome (HUS). Toddlers, who can have poor growth, progressive microcephaly, cytopenias (including megaloblastic anemia), global developmental delay, encephalopathy, and neurologic signs such as hypotonia and seizures. Adolescents and adults, who can have neuropsychiatric symptoms, progressive cognitive decline, thromboembolic complications, and/or subacute combined degeneration of the spinal cord. [from GeneReviews]
Authors:
Jennifer L Sloan  |  Nuria Carrillo  |  David Adams, et. al.   view full author information

Additional description

From OMIM
Homocystinuria and megaloblastic anemia is an autosomal recessive inborn error of metabolism resulting from defects in the cobalamin (vitamin B12)-dependent pathway that converts homocysteine to methionine, which is catalyzed by methionine synthase (MTR; 156570). Clinical features are somewhat variable, but include delayed psychomotor development, hypotonia, megaloblastic anemia, homocystinuria, and hypomethioninemia, all of which respond to cobalamin supplementation. Methylmalonic aciduria is not present. Two complementation groups have been described based on fibroblast studies: CblE and CblG (250940) (Watkins and Rosenblatt, 1988). Cells from patients with CblE fail to incorporate methyltetrahydrofolate into methionine in whole cells, but cell extracts show normal methionine synthase activity in the presence of a reducing agent. Cells from patients with CblG have defects in the methionine synthase enzyme under both conditions (summary by Leclerc et al., 1996). CblG is caused by mutation in the MTR gene.  http://www.omim.org/entry/236270

Clinical features

From HPO
Homocystinuria
MedGen UID:
42485
Concept ID:
C0019880
Disease or Syndrome
Homocystinuria is an inherited disorder in which the body is unable to process certain building blocks of proteins (amino acids) properly. \n\nThe most common form of homocystinuria, called classic homocystinuria, is characterized by tall stature, nearsightedness (myopia), dislocation of the lens at the front of the eye, a higher risk of blood clotting disorders, and brittle bones that are prone to fracture (osteoporosis) or other skeletal abnormalities. Some affected individuals also have developmental delay and learning problems.\n\nThe signs and symptoms of homocystinuria typically develop during childhood, although some mildly affected people may not show signs and symptoms until adulthood.\n\nLess common forms of homocystinuria can cause intellectual disability, slower growth and weight gain (failure to thrive), seizures, and problems with movement. They can also cause and a blood disorder called megaloblastic anemia, which occurs when a person has a low number of red blood cells (anemia), and the remaining red blood cells are larger than normal (megaloblastic).
Methylmalonic aciduria
MedGen UID:
343266
Concept ID:
C1855119
Disease or Syndrome
Increased concentration of methylmalonic acid in the urine.
Failure to thrive
MedGen UID:
746019
Concept ID:
C2315100
Disease or Syndrome
Failure to thrive (FTT) refers to a child whose physical growth is substantially below the norm.
Lethargy
MedGen UID:
7310
Concept ID:
C0023380
Sign or Symptom
A state of fatigue, either physical or mental slowness and sluggishness, with difficulties in initiating or performing simple tasks. Distinguished from apathy which implies indifference and a lack of desire or interest in the task. A person with lethargy may have the desire, but not the energy to engage in personal or socially relevant tasks.
Seizure
MedGen UID:
20693
Concept ID:
C0036572
Sign or Symptom
A seizure is an intermittent abnormality of nervous system physiology characterized by a transient occurrence of signs and/or symptoms due to abnormal excessive or synchronous neuronal activity in the brain.
Cerebral atrophy
MedGen UID:
116012
Concept ID:
C0235946
Disease or Syndrome
Atrophy (wasting, decrease in size of cells or tissue) affecting the cerebrum.
Global developmental delay
MedGen UID:
107838
Concept ID:
C0557874
Finding
A delay in the achievement of motor or mental milestones in the domains of development of a child, including motor skills, speech and language, cognitive skills, and social and emotional skills. This term should only be used to describe children younger than five years of age.
Gait disturbance
MedGen UID:
107895
Concept ID:
C0575081
Finding
The term gait disturbance can refer to any disruption of the ability to walk.
Intellectual disability, progressive
MedGen UID:
337397
Concept ID:
C1846149
Mental or Behavioral Dysfunction
The term progressive intellectual disability should be used if intelligence decreases/deteriorates over time.
Hyperkinetic movements
MedGen UID:
854367
Concept ID:
C3887506
Disease or Syndrome
Motor hyperactivity with excessive movement of muscles of the body as a whole.
Cerebral cortical atrophy
MedGen UID:
1646740
Concept ID:
C4551583
Disease or Syndrome
Atrophy of the cortex of the cerebrum.
Megaloblastic anemia
MedGen UID:
1527
Concept ID:
C0002888
Disease or Syndrome
Anemia characterized by the presence of erythroblasts that are larger than normal (megaloblasts).
Normocytic anemia
MedGen UID:
39310
Concept ID:
C0085577
Disease or Syndrome
A kind of anemia in which the volume of the red blood cells is normal.
Hypertonia
MedGen UID:
10132
Concept ID:
C0026826
Finding
A condition in which there is increased muscle tone so that arms or legs, for example, are stiff and difficult to move.
Hypotonia
MedGen UID:
10133
Concept ID:
C0026827
Finding
Hypotonia is an abnormally low muscle tone (the amount of tension or resistance to movement in a muscle). Even when relaxed, muscles have a continuous and passive partial contraction which provides some resistance to passive stretching. Hypotonia thus manifests as diminished resistance to passive stretching. Hypotonia is not the same as muscle weakness, although the two conditions can co-exist.
Methylmalonic acidemia
MedGen UID:
120654
Concept ID:
C0268583
Disease or Syndrome
For this GeneReview, the term "isolated methylmalonic acidemia" refers to a group of inborn errors of metabolism associated with elevated methylmalonic acid (MMA) concentration in the blood and urine that result from the failure to isomerize (convert) methylmalonyl-coenzyme A (CoA) into succinyl-CoA during propionyl-CoA metabolism in the mitochondrial matrix, without hyperhomocysteinemia or homocystinuria, hypomethioninemia, or variations in other metabolites, such as malonic acid. Isolated MMA is caused by complete or partial deficiency of the enzyme methylmalonyl-CoA mutase (mut0 enzymatic subtype or mut– enzymatic subtype, respectively), a defect in the transport or synthesis of its cofactor, 5-deoxy-adenosyl-cobalamin (cblA, cblB, or cblD-MMA), or deficiency of the enzyme methylmalonyl-CoA epimerase. Prior to the advent of newborn screening, common phenotypes included: Infantile/non-B12-responsive form (mut0 enzymatic subtype, cblB), the most common phenotype, associated with infantile-onset lethargy, tachypnea, hypothermia, vomiting, and dehydration on initiation of protein-containing feeds. Without appropriate treatment, the infantile/non-B12-responsive phenotype could rapidly progress to coma due to hyperammonemic encephalopathy. Partially deficient or B12-responsive phenotypes (mut– enzymatic subtype, cblA, cblB [rare], cblD-MMA), in which symptoms occur in the first few months or years of life and are characterized by feeding problems, failure to thrive, hypotonia, and developmental delay marked by episodes of metabolic decompensation. Methylmalonyl-CoA epimerase deficiency, in which findings range from complete absence of symptoms to severe metabolic acidosis. Affected individuals can also develop ataxia, dysarthria, hypotonia, mild spastic paraparesis, and seizures. In those individuals diagnosed by newborn screening and treated from an early age, there appears to be decreased early mortality, less severe symptoms at diagnosis, favorable short-term neurodevelopmental outcome, and lower incidence of movement disorders and irreversible cerebral damage. However, secondary complications may still occur and can include intellectual disability, tubulointerstitial nephritis with progressive impairment of renal function, "metabolic stroke" (bilateral lacunar infarction of the basal ganglia during acute metabolic decompensation), pancreatitis, growth failure, functional immune impairment, bone marrow failure, optic nerve atrophy, arrhythmias and/or cardiomyopathy (dilated or hypertrophic), liver steatosis/fibrosis/cancer, and renal cancer.
Hypomethioninemia
MedGen UID:
336368
Concept ID:
C1848555
Finding
A decreased concentration of methionine in the blood.
Decreased methionine synthase activity
MedGen UID:
376395
Concept ID:
C1848580
Finding
A reduction in methionine synthase activity.
Hyperhomocystinemia
MedGen UID:
812677
Concept ID:
C3806347
Finding
An increased concentration of homocystine in the blood.
Decreased circulating methylcobalamin concentration
MedGen UID:
867371
Concept ID:
C4021736
Finding
The concentration of methylcobalamin in the blood circulation is below the lower limit of normal. Methylcobalamin is a form of vitamin B12.
Nystagmus
MedGen UID:
45166
Concept ID:
C0028738
Disease or Syndrome
Rhythmic, involuntary oscillations of one or both eyes related to abnormality in fixation, conjugate gaze, or vestibular mechanisms.
Blindness
MedGen UID:
99138
Concept ID:
C0456909
Disease or Syndrome
Blindness is the condition of lacking visual perception defined as a profound reduction in visual perception. On the 6m visual acuity scale, blindness is defined as less than 3/60. On the 20ft visual acuity scale, blindness is defined as less than 20/400. On the decimal visual acuity scale, blindness is defined as less than 0.05. Blindness is typically characterized by a visual field of no greater than 10 degrees in radius around central fixation.

Recent clinical studies

Diagnosis

Kasapkara ÇS, Yılmaz-Keskin E, Özbay-Hoşnut F, Akçaboy M, Polat E, Olgaç A, Zorlu P
Turk J Pediatr 2019;61(2):282-285. doi: 10.24953/turkjped.2019.02.021. PMID: 31951343
Vilaseca MA, Vilarinho L, Zavadakova P, Vela E, Cleto E, Pineda M, Coimbra E, Suormala T, Fowler B, Kozich V
J Inherit Metab Dis 2003;26(4):361-9. doi: 10.1023/a:1025159103257. PMID: 12971424

Clinical prediction guides

Vilaseca MA, Vilarinho L, Zavadakova P, Vela E, Cleto E, Pineda M, Coimbra E, Suormala T, Fowler B, Kozich V
J Inherit Metab Dis 2003;26(4):361-9. doi: 10.1023/a:1025159103257. PMID: 12971424

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